The Chemistry fin designed by the Chem Crew. "The Chemistry "Colab 2" is a template that we designed for the high performance surfer who wants drive and the right amount of release. With it's wide base, smooth rake, and medium sized tip, The Colab 2 goes well in all types of surf. This fin is a med/large fin with a 4.49" base and 4.73" height." Honeycomb interior with carbon fiber inlay at the base to stiffen things up.